Comb polymers as blocking additives for swelling clays

ABSTRACT

A comb polymer, in particular for use as a clay-inerting agent, including: a) at least one poly(alkylene oxide) side chain-bearing monomer unit M1 without ionic groups, b) optionally at least one cationic monomer unit MC, c) optionally at least one anionic monomer unit MA, d) optionally, at least one non-ionic monomer unit M3, wherein the molar ratio of the cationic monomer units MC to the side chain-bearing monomer units M1 is equal to or less than 10, the molar ratio of the anionic monomer units MA to the side chain-bearing monomer units M1 is less than 1, preferably equal to or less than 0.5, and the molar ratio of the non-ionic monomer units M3 to the side chain-bearing monomer units M1 is less than 5.

TECHNICAL FIELD

The invention relates to a comb polymer, in particular for use as aclay-inerting agent. Additionally, the invention is concerned with a kitof parts and a composition comprising the comb polymer. Further aspectsof the invention are related to a method, in particular for plasticizinga mineral binder composition, as well as a use of a comb polymer as aclay-inerting agent.

BACKGROUND ART

Dispersants or superplasticizers are used in the building industry asplasticizers or water-reducing agents for mineral binder compositions,such as for example concrete, cement mortar, plaster or lime mortar. Thedispersants are generally organic polymers which are added to the mixingwater or admixed with the binder compositions in solid form. In thisway, it is advantageously possible to alter both, the consistency of thebinder composition during processing and the properties in the hardenedstate.

Known particularly effective dispersants are, for example, polymersbased on polycarboxylate ethers (PCE). Polymers of this kind have apolymer backbone and side chains bonded thereto. Corresponding polymersare described, for example, in EP 1 138 697 A1 (Sika AG).

High quality river sands, which are typically used as aggregates formortar or concrete production, are increasingly becoming a scarceresource. Thus, more and lower quality sands comprising unwantedimpurities or contaminants, either from natural sources or fromrecycling processes, have to be used.

Unfortunately, the presence of certain contaminants, such as e.g.swelling clays, even in very low amounts, has a huge impact on theeffectiveness of PCE-based admixtures in mortar or concrete production.

This is because PCEs intercalate in swelling clays and, thus, asignificant proportion of the added PCEs is lost and cannot adsorbanymore on cement or cement hydrates so that the desired water-reducingeffect cannot be achieved. Consequently, the flowability of mortar orconcrete with a given PCE dosage is significantly reduced if swellingclays are present.

Concrete producers are typically addressing this problem either by usinga higher PCE dosage to compensate the loss of PCE performance, or byadding special additives being able to reduce or block the influence ofswelling clays, i.e. so-called swelling clay blockers.

Although increasing the PCE dosage is in principle a straightforwardsolution, it is economically inefficient and can be problematic if theswelling clay content is fluctuating. In this case, the concreteproducer is constantly forced to adjust the PCE dosage in order to keepa certain flowability, which is highly time-consuming.

Regarding clay-blocking additives, there are various approaches knownnowadays. For example, WO 2010/005117 A1 (W.R. Grace) describes a methodin which polycationic compounds in combination with a hydroxycarboxylicacid or a salt thereof is used to enhance slump retention in cements andconcretes having clay-bearing aggregates, wherein the clay otherwiseabsorbs or diminishes the efficiency of polycarboxylatesuperplasticizers.

WO 2016/096970 A1 (BASF SE) describes a method of inhibiting theswelling of clay in subterranean formations with a polyimidazoliumcompound.

Additionally there are products on the market with swellingclay-blocking properties which are based on a strong water-reducingeffect. Products sold by BASF under the brand “MasterSuna” can bementioned here.

However, these approaches have to be improved regarding effectiveness,robustness toward fluctuations of swelling clays, compatibility withconcrete admixtures or lower chloride content.

There is thus a need to develop new and improved solutions which reduceor overcome the aforementioned drawbacks.

DISCLOSURE OF THE INVENTION

It is an objective of the present invention to provide substances andmethods which allow for reducing or preventing problems with swellingclays in mineral binder compositions. Desirably, the substances ormethods shall reduce the negative influence of swelling clays on theeffectiveness of dispersants, in particular of PCE-based dispersants.Preferably, the duration of action should be as long as possible.Especially, the substances or methods shall be as effective as possiblewhile having a best possible robustness. Preferably, the substances ormethods as such shall affect the flowability of mineral bindercompositions as little as possible. Also, preferably, the substances andmethods should be as insensitive as possible with regard to fluctuatingswelling clay contents in mineral binder compositions. Particularly, thesubstances or methods shall be compatible with common additives used forproducing mineral binder compositions, or with corresponding processes,respectively. Especially, the substances or methods shall be compatiblewith lignosulfonates, gluconates, naphthalenesulfonates, sulfonatednaphthalene-formaldehyde condensates, melamine sulfonates, vinylcopolymers, sulfonated vinyl copolymers, and/or polycarboxylates,especially polycarboxylate ethers. In particular, the substances ormethods shall be compatible with PCE-based dispersants. Also, thesubstances or methods should have a content of chloride as low aspossible or should be substantially free from chloride.

Surprisingly, it has been found that the problem of the invention can besolved by the features of claim 1. Thus, the core of the invention is acomb polymer, in particular for use as a clay-inerting agent,comprising:

-   a) at least one poly(alkylene oxide) side chain-bearing monomer unit    M1 without ionic groups,-   b) optionally at least one cationic monomer unit MC,-   c) optionally at least one anionic monomer unit MA,-   d) optionally, at least one non-ionic monomer unit M3,

wherein the molar ratio of the cationic monomer units MC to the sidechain-bearing monomer units M1 is equal to or less than 10, the molarratio of the anionic monomer units MA to the side chain-bearing monomerunits M1 is less than 1, preferably equal to or less than 0.5, and themolar ratio of the non-ionic monomer units M3 to the side chain-bearingmonomer units M1 is less than 5.

As has been shown, the inventive comb polymers allow for a highlyefficient reduction of the negative influence of swelling clays on theeffectiveness of dispersants, in particular of PCE-based dispersants, inmineral binder compositions containing swelling clays. Thereby, theinventive solution turned out to be highly robust and the comb polymersonly have little effect on the flowability of mineral bindercompositions. Specifically, the dosage of the comb polymer according tothe invention is rather uncritical, especially if a certain thresholdhas been reached. Therefore, fluctuating contents of swelling clays inmineral binder compositions are much less of an issue with the inventivecomb polymers. Thus, the comb polymers according to the invention can beused as clay-inerting or clay-blocking agents, especially in combinationwith PCE-based dispersants.

Specifically, the comb polymers according to the invention typicallyhave a rather high grafting density of poly(alkylene oxide) side chains,which is in particular higher than the grafting density of usualPCE-based dispersants. Without being bound by theory, it is believedthat comb polymers according to the invention intercalate in swellingclays via their side chains.

In view of this theory, single poly(alkylene oxide) side chains, such ase.g. methyl polyethylene glycols, which are not part of a comb polymerstructure should as well be good blocking additives. Nevertheless, itwas surprisingly found that the comb polymers according to the inventionare much better blocking additives when compared to single poly(alkyleneoxide) side chains. Even when using the same or higher dosages of singlepoly(alkylene oxide) side chains, these single side chains are not ableto reduce or prevent intercalation of PCE-based dispersants to the sameextent as the inventive comb polymers.

Moreover, the inventive comb polymers turned out to be at least asefficient as known blocking additives such as polycations or like knownblocking additives having a strong plasticizing effect.

Further aspects of the invention are the subject matter of otherindependent claims. Especially preferred embodiments of the inventionare the subject matter of the dependent claims.

WAYS OF CARRYING OUT THE INVENTION

A first aspect of the invention relates to a comb polymer, in particularfor use as a clay-inerting agent, comprising:

-   a) at least one poly(alkylene oxide) side chain-bearing monomer unit    M1 without ionic groups,-   b) optionally at least one cationic monomer unit MC,-   c) optionally at least one anionic monomer unit MA,-   d) optionally, at least one non-ionic monomer unit M3,

wherein the molar ratio of the cationic monomer units MC to the sidechain-bearing monomer units M1 is equal to or less than 10, especiallyless than 5, the molar ratio of the anionic monomer units MA to the sidechain-bearing monomer units M1 is less than 1, preferably equal to orless than 0.5, and wherein the molar ratio of the non-ionic monomerunits M3 to the side chain-bearing monomer units M1 is less than 5.

Thereby, the monomer units M1, MC, MA and M3 differ from each otherchemically and/or structurally. In particular, the at least onenon-ionic monomer unit M3 does note comprise poly(alkylene oxide)groups, especially it does not comprise poly(ethylene oxide) groups.

Within the present context, a “polymer” is a substance comprising orconsisting of at least 2, especially at least 3, preferably at least 5,polymerized monomer units.

A “comb polymer” is a polymer comprising a polymer backbone and sidechains bonded thereto.

The term “mineral binder” denotes a binder which reacts in the presenceof water in a hydration reaction to form solid hydrates or hydratephases. This can be, for example, a hydraulic binder, a latent hydraulicbinder, and/or a pozzolanic binder. Highly preferred are hydraulicbinders. Hydraulic binders can set under water. But it can also beadvantageous for the mineral binder to contain other binders in additionto or instead of a hydraulic binder. These are, in particular, latenthydraulic binders and/or pozzolanic binders. Suitable latent hydraulicand/or pozzolanic binders are, e.g., slag, fly ash, silica dust and/ornatural pozzolans.

In particular the mineral binder comprises or consists of cement,especially cement of type OEM I, OEM II, OEM III, OEM IV and/or OEM V(according to the standard EN 197-1).

In one preferred embodiment, with respect to the overall mineral bindercontent, the mineral binder contains at least 5 wt.-%, especially atleast 20 wt.-%, preferably at least 35 wt.-%, especially at least 65wt.-%, of hydraulic binder, especially cement, and, optionally, 5 to 95wt.-%, especially 5 to 65 wt.-%, particularly 15 to 35 wt.-%, of latenthydraulic and/or pozzolanic binder.

The terms “clay-inerting agent”, “clay-blocking agent” and “clayblocker” are meant to be agents capable of reducing or inhibitingadverse effects of swellable clays on the effectiveness of dispersants,in particular of PCE-based dispersants, in mineral binder compositions.

The terms “swelling clay” or “swelling clays” stand in particular forclay minerals which expand and/or increase their volume when wetted byaqueous solutions. Structurally talking, swelling clays are layeredsilicate minerals and, more specific, phyllosilicate minerals based ontetrahedral MO₄ sheets (M=Si⁴⁺, Al³⁺) and octahedral M(O,OH)₆ sheets(M=Al³⁺, Mg²⁺, Fe^(2+/3+), etc.). They differ from each other by theirway of stacking the tetrahedral and octahedral sheets, which stronglyinfluences their capacity of adding or losing water molecules or cationsfrom their structure. The most common swelling clays are part of the 2:1clay group. These are clays in which an octahedral sheet (O) issandwiched between two tetrahedral sheets (T) forming an elementaryunit, in this case a T-O-T layer. The elementary units are bound to eachother, forming a stack of layers. The bonding is a result of theformation of an interlayer between two elementary units, called theZ-sheet, which in swelling clays contains cations that will hold the twolayers together. As an example, in the non-swelling clay muscovite,potassium ions are located in the Z-layer. These potassium ions in 2:1clays can be lost due to weathering processes that form apotassium-depleted Z-sheet, which in aqueous solution will lead to anexpansion of the Z-layer. Additionally, potassium can be partly replacedby other ions like calcium, sodium or even other ions. Weathering ofrocks is an important natural process enhancing the formation of theseminerals. Swelling clays that can be formed are for example mineralsfrom the smectite group, such as montmorillonite, nontronite,beidellite, saponite, hectorite, sauconite. Other swelling clays, whichare not explicitly mentioned here, are also encompassed by the term“swelling clay”, e.g. vermiculites. After the weathering process of therocks, the swelling clays are mobilized and found in the aggregates,e.g. sand aggregates.

Thus, in particular, the comb polymers according to the presentinvention are used in compositions comprising such swelling clays,especially montmorillonite, nontronite, beidellite, saponite, hectorite,sauconite, and/or vermiculites.

Especially, the swellable clays are clays which are part of the 2:1 claygroup. Hence, in particular, the comb polymers according to the presentinvention are used in compositions comprising such swelling clays whichare part of the 2:1 clay group.

The terms “ionic group” or “ionic groups” especially mean groups that,at least at a pH>10, especially at least at a pH>12, are present innegatively charged form or in positively charged form. In the presentcontext, groups present in negatively charged form are called “anionicgroups”. Groups present in positively charged form are called “cationicgroups”. Thereby, counter ions which are solely bound by ionic bondingare not to be considered with regard to the charge of the ionic groups.

The terms “cationic monomers” and “cationic monomer units” especiallymean monomers or polymerized monomers that, at least at a pH>10,especially at least at a pH>12, are present in positively charged form.Thereby, counter ions which are bound by ionic bonding are not to beconsidered with regard to the charge of the “cationic monomers” or the“cationic monomer units”.

Likewise, the terms “anionic monomers” and “anionic monomer units”especially mean monomers or polymerized monomers that, at least at apH>10, especially at least at a pH>12, are present in negatively chargedform. Also in this case, counter ions which are bound by ionic bondingare not to be considered with regard to the charge of the “anionicmonomers” or the “anionic monomer units”.

Especially, anionic monomers are monomers comprising anionic groups suchas e.g. hydrogen donor groups or acid groups. The anionic groups aremore preferably acid groups, for example carboxylic acid, sulfonic acid,phosphoric acid and/or phosphonic acid groups. Preference is given tocarboxylic acid groups. The anionic groups or acid groups may also takethe form of anions in deprotonated form or of a salt with a counter ionor cation.

Cationic monomers are monomers comprising cationic groups. Thereby, thecationic group is covalently attached to the cationic monomer. It may bea common cationic group which can be attached to organic polymers, inparticular an ammonium, sulfonium and/or phosphonium group. The cationicgroups may also take the form of a salt with a counter ion or anion.

The cationic group is in particular grafted onto the backbone of thecomb polymer. This means that it is not part of the main chain orbackbone of the comb polymer. Therefore, it does not connect subunits ofthe main chain to one another. Thereby it differs, for example, from thecondensates of dimethylamine and epichlorohydrin of US 20070287794 A1.

The terms “non-ionic monomers” and “non-ionic monomer units” especiallymean monomers or polymerized monomers which do not have any ionicgroups, in particular they neither have any anionic groups nor anycationic groups. Especially, the non-ionic monomers, at a pH>10,especially at a pH>12, are present in uncharged form.

Also, the at least one poly(alkylene oxide) side chain-bearing monomerunit M1 does not comprise any ionic groups, in particular it neither hasany anionic groups nor any cationic groups. Especially, the at least onepoly(alkylene oxide) side chain-bearing monomer unit M1 does notcomprise any carboxylic acid, sulfonic acid, phosphoric acid, andphosphonic acid groups and/or the at least one poly(alkylene oxide) sidechain-bearing monomer unit M1 does not comprise any ammonium, sulfoniumand/or phosphonium groups, in particular quaternary ammonium groups.

Especially, the at least one poly(alkylene oxide) side chain-bearingmonomer unit M1, at a pH>10, especially at a pH>12, is present inuncharged form.

Especially, the at least one poly(alkylene oxide) side chain-bearingmonomer unit M1 is bonded to the polymer backbone via ester, ether,amide and/or imide groups. The at least one poly(alkylene oxide) sidechain-bearing monomer unit M1 preferably includes poly(ethylene oxide)side chains, poly(propylene oxide) side chains and/or poly(ethyleneoxide/propylene oxide) side chains. In particular, the number averagemolecular weight of the poly(alkylene oxide) side chains is in the rangeof 100-10′000 g/mol, especially 250-5′000 g/mol, preferably 500-3′500g/mol, in particular 900-2′500 g/mol, for example 950-1′500 g/mol or1′000-1′400 g/mol.

Particularly, the side chain-bearing monomer unit M1 includes astructure of the formula I:

where

-   -   R¹, and R², in each case independently, are H or an alkyl group        having 1 to 5 carbon atoms, preferably H or CH₃ or mixtures        thereof,    -   R³, in each case independently, is H, an alkyl group having 1 to        5 carbon atoms, preferably H or CH₃ or mixtures thereof, or a        group with formula —(CH₂)_(m)—[C═O]_(p)—X—R₄,    -   m=0, 1 or 2,    -   p=0 or 1,    -   X, in each case independently, is —O— or —NH—,    -   R⁴ is a group of the formula -[AO]n-R^(a)        -   where A=C₂- to C₄-alkylene, R^(a) is H, a C₁- to C₂₀-alkyl            group, -cycloalkyl group or -alkylaryl group,    -   and n=2-250, especially 10-200, in particular 15-50 or 20-25.

More particularly, R¹=H or CH₃ and R²=R³=H.

The X group in monomer units M1, advantageously in at least 75 mol %,particularly in at least 90 mol %, especially in at least 95 mol % or atleast 99 mol % of the total number of monomer units M1, is —O— (=oxygenatom).

In a further advantageous embodiment, m=0, p=1 and preferably X=—O—. Inthis case it is possible to prepare the copolymer on the basis of(meth)acrylic esters which are commercially available.

In another advantageous embodiment, m=0-2, p=0 and preferably X=—O—.Thereby, it is possible to prepare the copolymer on the basis of vinylether, (meth)allyl ether or isoprenyl ether monomers which arecommercially available.

In a particularly advantageous embodiment, R¹ is a mixture of 40-60 mol% of H and 40-60 mol % of —CH₃.

The R⁴ moiety in the side chain-bearing monomer units M1, based on thetotal number of R⁴ moieties in the monomer units, in particular consistsof a poly(ethylene oxide), especially to an extent of at least 50 mol %,especially at least 75 mol %, preferably at least 95 mol % or at least99 mol %.

The proportion of ethylene oxide units, based on the total number ofalkylene oxide units in the copolymer, is especially more than 75 mol %,especially more than 90 mol %, preferably more than 95 mol % andspecifically 100 mol %.

More particularly, R⁴ has essentially no hydrophobic groups, especiallyno alkylene oxides having three or more carbon atoms. This especiallymeans that the proportion of alkylene oxides having three or more carbonatoms based on the total number of alkylene oxides is less than 5 mol %,especially less than 2 mol %, preferably less than 1 mol % or less than0.1 mol %. In particular, there are no alkylene oxides having three ormore carbon atoms present, i.e. the proportion thereof is 0 mol %.

R^(a) is advantageously H and/or a methyl group. Particularlyadvantageously, A=C₂-alkylene and R^(a) is H or a methyl group.

More particularly, n=10-150, especially n=15-100, preferably n=17-70,specifically n=19-45 or n=20-25. In particular, this achieves excellentblocking effects.

Particular preference is given to copolymers in which R¹ is selectedfrom the group consisting of H, —CH₃, and mixtures thereof; R² and R³=H;R⁴, based on the total number of R⁴ moieties in the monomer units,consists of a poly(ethylene oxide) especially to an extent of at least50 mol %, especially at least 75 mol %, preferably at least 95 mol % orat least 99 mol %; and X in at least 75 mol %, particularly in at least90 mol %, especially in at least 99 mol %, of the total number ofmonomer units M1 is —O—.

According to a preferred embodiment, the cationic group of the cationicmonomer unit MC in the comb polymer includes or consists of an ammoniumgroup, a sulfonium group and/or or a phosphonium group, in particular aquaternary ammonium group.

In a preferred embodiment of the invention, the cationic group is anammonium group. Particularly preferably it is a quaternary ammoniumgroup. In this case, a positively charged nitrogen atom is substitutedwith four organic groups Preferably, the cationic group has formula—N⁺R¹⁰R¹¹R¹², wherein R¹⁰, R¹¹ and R¹² are independently of one anotherH, an aliphatic hydrocarbon moiety having 1 to 20 C atoms, acycloaliphatic hydrocarbon moiety having 5 to 8 C atoms and/or an arylmoiety having 6 to 14 C atoms. As indicated by the hyphen, thepositively charged nitrogen atom in the group of formula —N⁺R¹⁰R¹¹R¹² ischemically or covalently bonded, optionally via a chemical linker group,to the cationic monomer. Preferably, R¹⁰, R¹¹ and R¹² are not H,particularly preferably selected from methyl and ethyl.

Especially, the cationic monomer unit MC in the polymer includes orconsists of a cationic monomer which has a structure of the formula II:

where

-   -   R⁵, in each case independently, is -[D]_(d)-[E]_(e)—F, with        -   D=—(COO)— and/or —(CONH)—,        -   E=an alkylene group having 1 to 5 carbon atoms,        -   F=—N⁺R¹⁰R¹¹R¹², —S⁺R¹⁰R¹¹R¹² and/or —P⁺R¹⁰R¹¹R¹²,        -   wherein R¹⁰, R¹¹ and R¹² are independently of one another H,            an aliphatic hydrocarbon moiety having 1 to 20 C atoms, a            cycloaliphatic hydrocarbon moiety having 5 to 8 C atoms            and/or an aryl moiety having 6 to 14 C atoms;        -   whereby        -   d=0 or 1,        -   e=0 or 1,    -   R⁶, R⁷ and R⁸, in each case independently, are H or an alkyl        group having 1 to 5 carbon atoms.

Thereby, preferably, R⁶=H or CH₃, R⁷=R⁸=H, d=1 and, especiallyD=—(COO)—.

According to a preferred embodiment, F=—N⁺R¹⁰R¹¹R¹², e=1 and, preferablyE=an alkylene group having 2 to 3 carbon atoms.

In a preferred embodiment of the invention, the ionic monomer isselected from [2-(acryloyloxy)-ethyl]trimethylammonium chloride,[2-(acryloylamino)-ethyl]trimethylammonium chloride,[2-(acryloyloxy)-ethyl]trimethy-lammoniummethosulfate,[2-(methacryloyloxy)-ethyl]trimethylammonium chloride or methosulfate,[3-(acryloylamino)-propyl]trimethylammonium chloride,[3-(methacryloylamino)-propyl]trimethylammonium chloride.

Particularly advantageous according to the invention proved to be theuse of [2-(methacryloyloxy)-ethyl]trimethylammonium salts, in particularthe chloride. The use is commercially available from Evonik Industries,DE (under the brand name “Visiomer TMAEMC”) or from Sigma-Aldrich, DE.

According to another preferred embodiment, the comb polymer isessentially free of a cationic monomer unit MC. This means that aproportion of cationic monomer units MC in the comb polymer is 0-1mol-%, especially 0-0.1 mol-%, preferably 0 mol-%, with respect to thetotal number of monomer units present in the comb polymer.

In a further preferred embodiment, an anionic group of the anionicmonomer unit MA in the comb polymer includes or consists of a carboxylicacid, sulfonic acid, phosphoric acid and/or phosphonic acid group.

Preferably, the anionic monomer unit MA in the polymer includes orconsists of an anionic monomer which has a structure of the formula III

where

-   -   R¹³, in each case independently, is —COOM, —SO₂-OM, —O—PO(OM)₂        and/or —PO(OM)₂,    -   R¹⁴ and R¹⁵, in each case independently, are H or an alkyl group        having 1 to 5 carbon atoms,    -   R¹⁶, in each case independently, are H, —COOM or an alkyl group        having 1 to 5 carbon atoms,    -   or where R¹³ forms a ring together with R¹⁶ to give —CO—O—CO—,    -   M independently from each other is H⁺, an alkali metal ion, an        alkaline earth metal ion, a di- or trivalent metal ion, an        ammonium ion and an organic ammonium group.

More particularly, R¹³=COOM, R¹⁴=H or CH₃, R¹⁵=R¹⁶=H. It is thuspossible to prepare the copolymer on the basis of acrylic or methacrylicacid monomers, which is of interest from an economic point of view.

Likewise advantageously, R¹³=COOM, R¹⁴=H, R¹⁵=H and R¹⁶=COOM.Corresponding comb polymers can be prepared on the basis of maleic acidmonomers.

According to another preferred embodiment, the comb polymer isessentially free of an anionic monomer unit MA. This means that aproportion of anionic monomer units MA in the comb polymer is 0-1 mol-%,especially 0-0.1 mol-%, preferably 0 mol-%, with respect to the totalnumber of monomer units present in the comb polymer.

It may further be advantageous if the comb polymer comprises at leastone further non-ionic monomer unit M3 which especially differschemically and/or structurally from the monomer units M1, MC and MA. Inparticular, multiple different further monomer units M3 may be present.In this way, it is possible to further modify the properties of the combpolymer and to adjust them, for example, with regard to specificapplications.

Particularly advantageously, the non-ionic monomer unit M3 a monomerunit of the formula IV:

where R^(5′), R^(6′), R^(7′) are the same as defined for R⁶, R⁷ and R⁸,and m′ and p′ are the same as defined for m and p as described above inthe context of the copolymer;

-   -   Y, in each case independently, is a chemical bond or —O—;    -   Z, in each case independently, is a chemical bond, —O— or —NH—;    -   R²⁰, in each case independently, is an alkyl group, cycloalkyl        group, alkylaryl group, aryl group, hydroxyalkyl group or        acetoxyalkyl group, each having 1-20 carbon atoms.

Advantageous examples of non-ionic monomer units M3 are those wherem′=0, p′=0, Z and Y represent a chemical bond and R²⁰ is an alkylarylgroup having 6-10 carbon atoms.

Also suitable are especially further monomer units M3 in which m′=0,p′=1, Y is —O—, Z represents a chemical bond and R²⁰ is an alkyl grouphaving 1-4 carbon atoms.

Further suitable are further monomer units M3 where m′=0, p′=1, Y is achemical bond, Z is —O— and R²⁰ is an alkyl group and/or a hydroxyalkylgroup having 1-6 carbon atoms.

Particularly advantageously, the non-ionic monomer unit M3 consists ofpolymerized vinyl acetate, styrene and/or hydroxyalkyl (meth)acrylate,especially styrene.

According to another preferred embodiment, the comb polymer isessentially free of a non-ionic monomer unit M3. This means that aproportion of non-ionic monomer units M3 in the comb polymer is 0-1mol-%, especially 0-0.1 mol-%, preferably 0 mol-%, with respect to thetotal number of monomer units present in the comb polymer.

According to a preferred embodiment, the comb polymer, with respect tothe total number of monomer units present in the comb polymer, comprises20-100 mol-%, in particular 50-100 mol-%, especially 65-100 mol-%, forexample 80-100 mol-% or 95-100 mol-%, of the at least one poly(alkyleneoxide) side chain-bearing monomer unit M1.

Especially, a preferred comb polymer, with respect to the total numberof monomer units present in the comb polymer, comprises:

-   a) 95-100 mol-%, especially 97-100 mol-%, particularly or 98-100    mol-%, preferably 99.5 mol-%, of the at least one poly(alkylene    oxide) side chain-bearing monomer unit M1,-   b) 0-1 mol-%, especially 0-0.1 mol-%, preferably 0 mol-%, of the at    least one cationic monomer unit MC,-   c) 0-1 mol-%, especially 0-0.1 mol-%, preferably 0 mol-%, of the at    least one anionic monomer unit MA,-   d) 0-1 mol-%, especially 0-0.1 mol-%, preferably 0 mol-%, of the at    least one non-ionic monomer unit M3.

In such or other preferred comb polymers,

-   -   the molar ratio of the cationic monomer units MC to the side        chain-bearing monomer units M1 is equal to or less than 0.5,        especially less than or equal to 0.1, in particular less than or        equal to 0.01 or 0.    -   the molar ratio of the anionic monomer units MA to the side        chain-bearing monomer units M1 is equal to or less than 0.5,        especially less than or equal to 0.1, in particular less than or        equal to 0.01 or 0.    -   the molar ratio of the non-ionic monomer units M3 to the side        chain-bearing monomer units M1 is equal to or less than 0.5,        especially less than or equal to 0.1, in particular less than or        equal to 0.01 or 0.

In particular, the comb polymer, with respect to the total number ofmonomer units present in the comb polymer, comprises 100 mol-% of the atleast one poly(alkylene oxide) side chain-bearing monomer unit M1. Inthis case, the comb polymer can be a homopolymer of identical sidechain-bearing monomeric units M1 or a copolymer of at least twodifferent side chain-bearing monomeric units M1.

Such comb polymers are for example preferred if the comb polymercomprises side chain-bearing monomer units M1 including or consisting ofa structure of formula I as shown above wherein parameter p is equalto 1. These are for example poly(alkylene oxide) (meth)acrylate basedmonomer units M1.

According to another preferred embodiment, the comb polymer essentiallyconsists of the at least one poly(alkylene oxide) side chain-bearingmonomer unit M1 and the non-ionic monomer unit M3. In this case the combpolymer is a copolymer based on the at least one side chain-bearingmonomeric units M1 and the non-ionic monomer unit M3.

Such comb polymers are for example preferred if the comb polymercomprises side chain-bearing monomer units M1 including or consisting ofa structure of formula I as shown above wherein parameter p is equal to0. These are for example poly(alkylene oxide) alkenyl ether-basedmonomer units M1.

For example, a preferred comb polymer, with respect to the total numberof monomer units present in the comb polymer, comprises:

-   a) 30-70 mol-%, especially 40-60 mol-%, particularly or 40-50 mol-%,    of the at least one poly(alkylene oxide) side chain-bearing monomer    unit M1, and-   b) 0-1 mol-%, especially 0-0.1 mol-%, preferably 0 mol-%, of the at    least one cationic monomer unit MC,-   c) 0-1 mol-%, especially 0-0.1 mol-%, preferably 0 mol-%, of the at    least one anionic monomer unit MA,-   d) 30-70 mol-%, especially 40-60 mol-%, particularly or 40-50 mol-%,    of the at least one non-ionic monomer unit M3.

In such or other preferred comb polymers,

-   -   the molar ratio of the cationic monomer units MC to the side        chain-bearing monomer units M1 is equal to or less than 0.5,        especially less than or equal to 0.1, in particular less than or        equal to 0.01 or 0.    -   the molar ratio of the anionic monomer units MA to the side        chain-bearing monomer units M1 is equal to or less than 0.5,        especially less than or equal to 0.1, in particular less than or        equal to 0.01 or 0.    -   the molar ratio of the non-ionic monomer units M3 to the side        chain-bearing monomer units M1 is 0.1-5, especially 0.5-2.5, in        particular 0.8-2 or 1-1.5.

In a further preferred embodiment, the comb polymer comprises the atleast one cationic monomer MC. Thereby, preferably, the comb polymerconsists to an extent of at least 30 mol %, particularly at least 50 mol%, in particular at least 65 mol %, especially at least 90 mol % or 95mol %, of side chain-bearing monomer units M1 and the cationic monomerunits MC, with respect to the total number of monomer units present inthe comb polymer. The remaining monomer units can e.g. be the non-ionicmonomer units M3. Especially, the comb polymer consists of the at leastone poly(alkylene oxide) side chain-bearing monomer units M1 and the atleast one cationic monomer units MC.

For example, a further preferred comb polymer, with respect to the totalnumber of monomer units present in the comb polymer, comprises:

-   a) 10-99 mol-%, especially 40-95 mol-%, particularly or 50-75 mol-%,    of the at least one poly(alkylene oxide) side chain-bearing monomer    unit M1, and-   b) 1-90 mol-%, especially 5-60 mol-%, preferably 25-50 mol-%, of the    at least one cationic monomer unit MC,-   c) 0-1 mol-%, especially 0-0.1 mol-%, preferably 0 mol-%, of the at    least one anionic monomer unit MA,-   d) 0-75 mol-%, especially 5-60 mol-%, particularly 25-50 mol-% or 0    mol-%, of the at least one non-ionic monomer unit M3.

In such or other preferred comb polymers,

-   -   the molar ratio of the cationic monomer units MC to the side        chain-bearing monomer units M1 is 0.1-5, especially 0.5-2.5, in        particular 0.8-2 or 1-1.5,    -   the molar ratio of the anionic monomer units MA to the side        chain-bearing monomer units M1 is equal to or less than 0.5,        especially less than or equal to 0.1, in particular less than or        equal to 0.01 or 0,    -   the molar ratio of the non-ionic monomer units M3 to the side        chain-bearing monomer units M1 is 0-5, especially 0.1-2.5, in        particular 0.5-2 or 0.8-1.5.

Thereby, in particular, the molar ratio of the anionic monomer units MAto the cationic monomer units MC is in the range of 0-1, especially0-0.9, in particular 0-0.5 or 0-0.05.

In an especially preferred embodiment, the comb polymer is a blockcopolymer, whereby at least 75 mol-%, especially at least 90 mol-%,preferably at least 99 mol-%, of the total number of at least one sidechain-bearing monomer units M1 are arranged in a first block of theblock copolymer.

In particular, the block copolymer comprises a second block in which atleast 75 mol-%, especially at least 90 mol-%, preferably at least 99mol-%, of the total number of at least one cationic monomer units MC arearranged.

In a further preferred embodiment, between the first block and thesecond block, there is a third block comprising at least one sidechain-bearing monomer unit M1, at least one cationic monomer unit MCand/or at least one non-ionic monomer unit M3. Especially, the thirdblock has a non-random distribution of the monomer units M1 and/or thecationic monomer units MC in a direction along the polymer backbone.

A “non-random distribution” is understood in the present case to mean anon-statistical distribution of the monomer units M1 and/or the monomerunits MC. This means that the side chain-bearing monomer units M1 and/orthe ionic units MC are arranged in the third block, for example, in analternating manner and/or in a gradient structure.

The structure of the copolymers can be analyzed and determined, forexample, by nuclear magnetic resonance spectroscopy (NMR spectroscopy).By ¹³C and ¹H NMR spectroscopy in particular, the sequence of themonomer units in the copolymer can be determined on the basis ofneighboring group effects in the copolymer and by using statisticalevaluations.

In all of the structures described above, non-ionic monomer units M3 maybe added, for example in order to control the density of the othermonomeric units in the comb polymer and/or in order to adjust the combpolymer for specific needs.

Preferably, if used, the molar proportion of the non-ionic monomer unitsM3, with respect to the total number of the monomeric units in the combpolymer, is from 0.0001-50 mol-%, in particular 0.0002-30 mol-%,especially 0.001-25 mol-%, advantageously 0.1-10 mol-% or 1-9 mol-%.This is in particular valid for block copolymers.

The comb polymer is especially prepared by free-radical polymerization,e.g. by conventional free-radical polymerization or by controlledfree-radical polymerization (also called living free-radicalpolymerization). These polymerization techniques are well known to theskilled person.

Thereby, unilaterally ethylenically unsaturated poly(alkylene oxide)side chain-bearing monomer units M1′ according to formula V, optionallyat least one unilaterally ethylenically unsaturated ionic monomer unitMC′ and/or MA′ according to formula VI and/or VII and, optionally, atleast one unilaterally ethylenically unsaturated non-ionic monomer unitM3′ according to formula VIII, are polymerized together such that themolar ratio of the cationic monomer units MC to the side chain-bearingmonomer units M1 is equal to or less than 10, especially less than 5,the molar ratio of the anionic monomer units MA to the sidechain-bearing monomer units M1 is less than 1, preferably equal to orless than 0.5, and the molar ratio of the non-ionic monomer units M3 tothe side chain-bearing monomer units M1 is less than 5.

Thereby, R¹-R¹⁶, R^(5′)-R^(7′), R²⁰, X, Y, Z, m, m′, n and p, p′ aredefined as described above.

Among controlled free-radical polymerization techniques, reversibleaddition-fragmentation chain-transfer polymerization (RAFT),nitroxide-mediated polymerization (NMP) and/or atom transfer radicalpolymerization (ATRP) can be used.

In reversible addition-fragmentation chain-transfer polymerization,control over the polymerization is achieved by a reversible chaintransfer reaction. Specifically, a growing free-radical chain adds towhat is called a RAFT agent, which leads to formation of an intermediatefree radical. The RAFT agent then fragments, in such a way as to reformanother RAFT agent and a free radical available for propagation. In thisway, the probability of propagation is distributed uniformly over allchains. The average chain length of the polymer formed is proportionalto the RAFT agent concentration and to the reaction conversion. RAFTagents used are especially organic sulfur compounds. Particularlysuitable are dithioesters, dithiocarbamates, trithiocarbonates and/orxanthates. The polymerization can be initiated in a conventional mannerby means of initiators or thermal self-initiation.

In nitroxide-mediated polymerization, nitroxides react reversibly withthe active chain end to form what is called a dormant species. Theequilibrium between active and inactive chain ends is strongly to theside of the dormant species, which means that the concentration ofactive species is very low. The probability of two active chains meetingand terminating is thus minimized. An example of a suitable NMP agent isthe substance with Chemical Abstract number 654636-62-1, commerciallyavailable e.g. under the tradename “Blockbuilder MA”.

In atom transfer radical polymerization (ATRP), the concentration offree radicals is lowered by addition of a transition metal complex and acontrolling agent (halogen-based) to such an extent that chaintermination reactions, such as disproportionation or recombination, arevery substantially suppressed.

In the present context, reversible addition-fragmentation chain-transferpolymerization (RAFT) has been found to be particularly preferable,especially if block copolymers are to be produced.

The initiator used for the polymerization is more preferably an azocompound and/or a peroxide as free-radical initiator, which is at leastone representative selected from the group consisting of dibenzoylperoxide (DBPO), di-tert-butyl peroxide, diacetyl peroxide,azobisisobutyronitrile (AIBN), α,α′-azodiisobutyramidine dihydrochloride(AAPH) and/or azobisisobutyramidine (AIBA).

If the polymerization is effected in an aqueous solution or in water,α,α′-azodiisobutyramidine dihydrochloride (AAPH) is advantageously usedas initiator.

For control of the polymerization, in particular, one or morerepresentatives from the group consisting of dithioesters,dithiocarbamates, trithiocarbonates and/or xanthates are used.

It has additionally been found to be advantageous if the polymerizationis effected at least partly, preferably fully, in an aqueous solution.

In a second method known as polymer-analogous reaction, a polycarboxylicacid backbone is synthesized in a first step. Subsequently, side chainsare attached to the polycarboxylic acid backbone, for example byesterification, amidation or etherisation reactions with alcohols,amines and the like. Such polymer-analogous reactions, as well asresulting comb polymers, are described, for example, in WO 97/35814, WO95/09821, DE 100 15 135 A1, EP 1 138 697 A1, EP 1 348 729 A1 and WO2005/090416. Details about the polymer-analogous reaction are disclosed,for example, in EP 1 138 697 B1 on page 7, line 20 to page 8, line 50,as well as in its Examples, or in EP 1 061 089 B1 on page 4, line 54 topage 5, line 38 as well as in its Examples.

For formation of copolymers having block and/or gradient structures,unilaterally ethylenically unsaturated poly(alkylene oxide) sidechain-bearing monomer units M1′ and ethylenically unsaturated ionicmonomer units MC′ and/or MA′ and/or the ethylenically unsaturatednon-ionic monomer units M3′ are preferably at least partly added atdifferent times.

In a further preferred embodiment, in the polymerization, in a firststep a), a portion of the monomer units M1′ is converted or polymerizedand, after reaching a predetermined conversion, in a second step b), theas yet unconverted monomer units M1′ (if present) are polymerizedtogether with ionic monomer unit MC′ and/or MA′ and/or the non-ionicmonomer unit M3′. Step a) is especially effected essentially in theabsence of ionic monomer units MC′ and/or MA′ and M3′.

In this way, in a simple and inexpensive manner, a copolymer having asection consisting essentially of polymerized monomer units M1′ followedby a section having a gradient structure is preparable.

It is advantageous here to conduct steps a) and b) in immediatesuccession. In this way, it is possible to maintain the polymerizationreaction in steps a) and b) to the best possible degree.

The polymerization in step a) is especially conducted until 0.1-100 mol%, especially 1-95 mol %, preferably 10-90 mol %, in particular 25-85mol %, especially 60-85 mol % of monomer units M1′ have been convertedor polymerized.

The conversion of the monomers or the progress of the polymerization canbe monitored in a manner known per se, for example, with the aid ofliquid chromatography, especially high-performance liquid chromatography(HPLC).

A further aspect of the present invention is related to a kit of partscomprising a comb polymer as described above and a plasticizer formineral binder compositions. Thereby, plasticizer and comb polymerdiffer from a chemical and/or structural point of view. The kit of partscan also be present in the form of a premixed composition comprising thecomb polymer and the plasticizer for mineral binder compositions.

What is meant by the term “plasticizer” in the present context isespecially a substance which is capable of improving the flowability ofmineral binder compositions, e.g. mortar and/or cement compositionswhich have been mixed with water, and/or of reducing the waterrequirement of such compositions. Substances of this kind are alsoreferred to as “superplasticizers”.

More particularly, the plasticizer comprises at least one representativefrom the group consisting of lignosulfonates, gluconates,naphthalenesulfonates, sulfonated naphthalene-formaldehyde condensates,melamine sulfonates, vinyl copolymers, sulfonated vinyl copolymers,polycarboxylates, especially polycarboxylate ethers, or mixturesthereof.

More particularly, the plasticizer is a polycarboxylate, especially apolycarboxylate ether. It is more preferably a comb polymer having apolycarboxylate backbone and polyether side chains, where the polyetherside chains are bonded to the polycarboxylate backbone via ester, ether,amide and/or imide groups. More particularly, the polycarboxylate has arandom, statistical, blockwise, alternating or gradient-like monomerdistribution.

More preferably, the superplasticizer is a polymer P having orconsisting of the following substructure units:

-   -   a) a molar parts of a substructure unit S1 of the formula X

-   -   b) b molar parts of a substructure unit S2 of the formula XI

-   -   c) c molar parts of a substructure unit S3 of the formula (XII)

-   -   d) d molar parts of a substructure unit S4 of the formula (XIII)

-   -   where    -   L independently represents H+, an alkali metal ion, alkaline        earth metal ion, a di- or trivalent metal ion, an ammonium ion        or an organic ammonium group,    -   each R^(u) independently of the others is hydrogen or a methyl        group,    -   each R^(v) independently of the others is hydrogen or COOM,    -   r=0, 1 or 2,    -   t=0 or 1,    -   G¹ and G² is independently a C₁- to C₂₀-alkyl group, -cycloalkyl        group, -alkylaryl group or is -[A′O]_(s)-G⁴,        -   where A′=C₂ ⁻to C₄-alkylene, G⁴ is H, a C₁- to C₂₀-alkyl            group, -cycloalkyl group or -alkylaryl group,        -   and s=2-250,    -   G³ is independently NH₂, —NG⁵G⁶, —OG⁷NG⁸G⁹,        -   where G⁵ and G⁶ are independently            -   a C₁- to C₂₀-alkyl group, -cycloalkyl group, -alkylaryl                group or -aryl group,            -   or are a hydroxyalkyl group or are an acetoxyethyl group                (CH₃—CO—O—CH₂—CH₂—) or a hydroxyisopropyl group                (HO—CH(CH₃)—CH₂—) or an acetoxyisopropyl group                (CH₃—CO—O—CH(CH₃)—CH₂—);        -   or G⁵ and G⁶ together form a ring of which the nitrogen is            part, in order to construct a morpholine or imidazoline            ring;        -   G⁷ is a C₂-C₄-alkylene group,        -   G⁸ and G⁹ each independently represent a C₁- to C₂₀-alkyl            group, -cycloalkyl group, -alkylaryl group, -aryl group or a            hydroxyalkyl group,    -   and where a, b, c and d represent molar proportions of the        respective substructure units S1, S2, S3 and S4, with    -   a/b/c/d=(0.1-0.9)/(0.1-0.9)/(0-0.8)/(0-0.8),    -   especially a/b/c/d=(0.3-0.9)/(0.1-0.7)/(0-0.6)/(0-0.4),    -   preferably a/b/c/d=(0.5-0.8)/(0.2-0.4)/(0.001-0.005)/0    -   and with the proviso that a+b+c+d=1.

The sequence of the substructure units S1, S2, S3 and S4 may bealternating, blockwise or random. It is also possible that the one ormore substructure units S1, S2, S3 and S4 form a gradient structure. Inprinciple, it is also possible that further structural units are presentin addition to the substructure units 51, S2, S3 and S4. In particular,the sequences of the substructure units S1, S2, S3 and S4 in the polymerP are random or statistical.

Preferably, the substructure units 51, S2, S3, and S4 together have aproportion of at least 50% by weight, especially at least 90% by weight,most preferably at least 95% by weight, of the total weight of thepolymer P.

In the polymer P, R″ especially represents hydrogen and R^(u) ispreferably hydrogen and/or a methyl group.

Preferably, in the polymer P, r=0 and t=1. Also advantageously, r=1-2and t=0.

More particularly, in the polymer P, R″ is hydrogen, R^(u) is a methylgroup, r=1-2 and t=0.

G¹ and/or G² in the polymer P, in each case independently, areadvantageously -[A′O]_(s)-G⁴ with s=8-200, especially 20-70, and A′ is aC₂- to C₄-alkylene.

In the polymer P, G⁴, in each case independently, is preferably hydrogenor a methyl group.

Especially, a ratio a/b in polymer P is greater than the ratio ofmonomeric units MC/M1 and/or a ratio of MA/M1 in the comb polymerdescribed above. In particular the ratio a/b in polymer P is in therange of 1-10, in particular 1.5-5, especially 2-4.

Very particularly advantageous polymers P are those where

-   a) the R^(u) and R^(v) moieties are hydrogen,-   b) r=0,-   c) t=1,-   d) G¹ and G², in each case independently, are -[A′O]_(s)-G⁴ with    s=20-70 and A′=C₂-alkylene,-   e) G⁴ represents a methyl group and/or-   f) a/b/c/d=(0.5-0.8)/(0.2-0.4)/(0.001-0.005)/0

Likewise advantageous polymers P are those where

-   a) t=0 and r=1-2,-   b) G¹, in each case independently, is -[A′O]s-G⁴ with s=8-200,    especially 20-70,-   c) G⁴ represents hydrogen or a methyl group, especially hydrogen,-   d) and/or A′ is a C₂- to C₄-alkylene, especially a C₂-alkylene.

A weight-average molecular weight (Mw) of the polymer P is particularlyin the range of 5′000-150′000 g/mol, preferably 10′000-100′000 g/mol,especially 20′000-90′000 g/mol. The weight-average molecular weight (Mw)is determined by gel permeation chromatography (GPC), using polyethyleneglycol (PEG) as standard.

The preparation of polymers P is known per se to the person skilled inthe art. Corresponding superplasticizers or polymers P are alsocommercially supplied by Sika Schweiz AG under the ViscoCrete® tradename series.

A further aspect of the present invention is a composition comprising acomb polymer as described above and further comprising a mineral binder,aggregates, a plasticizer and/or swellable clays. Thus, the comb polymercan be present in premixed form together with at least one of thesecomponents, or the comb polymer is present in a mineral bindercomposition mixed with water.

Especially, the composition comprises the comb polymer as describedabove, a mineral binder, aggregates, and swellable clays. In particular,a plasticizer is present as well. Especially, the swellable clays areclays which are part of the 2:1 clay group.

Moreover the present invention is concerned with a method comprising thesteps of adding to a composition comprising swellable clays, especiallya mineral binder composition comprising swellable clays:

(i) a comb polymer as described above, and

(ii) a plasticizer as described above.

Preferably, the addition of the comb polymer is effected before theaddition of the plasticizer. However, it is for example also possible toadd the comb polymer and the plasticizer simultaneously. Especially, theswellable clays are clays which are part of the 2:1 clay group.

A further aspect of the present invention is related to the use of acomb polymer as described above as a clay-inerting agent and/or forreducing or inhibiting adverse effects of swellable clays on theeffectiveness of dispersants, in particular of PCE-based dispersants, inmineral binder compositions comprising swellable clays. Thereby, thecomb polymer can e.g. be used to increase the flowability and/or theprocessing time of mineral binder compositions comprising swellableclays and a dispersant, in particular a PCE-based dispersant.Especially, the swellable clays are clays which are part of the 2:1 claygroup.

Further advantageous embodiments and combinations of features of theinvention will emerge from the following exemplary embodiments and thetotality of the patent claims.

EXEMPLARY EMBODIMENTS

1. Preparation Examples of Comb Polymers

1.1 Comb Polymer P1 (Non-Ionic Homopolymer)

For the preparation of a non-ionic homopolymer by means of controlledfree polymerization, a round-bottom flask equipped with a refluxcondenser, stirrer system, thermometer and a gas inlet tube wasinitially charged with 57.4 g of 50% methoxy polyethylene glycol₁₀₀₀methacrylate (0.027 mol; average molecular weight: 1′000 g/mol; ˜20ethylene oxide units per molecule) and 18 g of deionized water. Thereaction mixture was heated to 80° C. with vigorous stirring. A gentleinert N₂ gas stream is passed through the solution during the wholereaction time. 378 mg of 4-cyano-4-(thiobenzoylthio)pentanoic acid (1.35mmol) were then added to the mixture. Once the substance had fullydissolved, 67 mg of AIBN (0.41 mmol) were added. From then on, theconversion was regularly checked by means of HPLC.

When the conversion, based on methoxy polyethylene glycol methacrylate,had reached 90%, the reaction was stopped. A clear, reddish, aqueoussolution was obtained having a solids content of around 40 wt. % whichwas diluted with water to obtain a solids content of around 30 wt. %.

The comb polymer thus obtained is a homopolymer comprising about 20 sidechain-nearing monomeric units and is referred to as comb polymer P1.

1.2 Comb Polymer P2 (Non-Ionic Homopolymer)

For the preparation of a non-ionic homopolymer by conventional freeradical polymerization, a round-bottom flask equipped with a refluxcondenser, stirrer system, thermometer and a gas inlet tube wasinitially charged with 186 g of deionized water. At a temperature of100° C., 796 g of 50% methoxy polyethylene glycol₁₀₀₀ methacrylate (0.37mol, average molecular weight: 1′000 g/mol; ˜20 ethylene oxide units permolecule) was added within 180 minutes. Additionally a solution of 4.5 gsodium hypophosphite and 6.7 g of water was added within 175 minutes anda solution of 0.93 g sodium persulfate and 5.0 g water was added within190 minutes. Once all the solutions were added, the reaction mixture wascooled down. A clear, colorless solution was obtained having a solidscontent of around 40 wt. % which was diluted with water to obtain asolids content of around 30 wt. %.

This polymer is referred to as comb polymer P2.

1.3 Comb Polymer P3 (Cationic Block Copolymer)

For the preparation of a cationic copolymer by means of controlled freeradical polymerization, a round-bottom flask equipped with a refluxcondenser, stirrer system, thermometer and a gas inlet tube wasinitially charged with 57.4 g of 50% methoxy polyethylene glycol₁₀₀₀methacrylate (0.027 mol; average molecular weight: 1′000 g/mol; ˜20ethylene oxide units per molecule) and 28.3 g of deionized water. Thereaction mixture was heated to 80° C. with vigorous stirring. A gentleinert N₂ gas stream was passed through the solution during the wholereaction time. 378 mg of 4-cyano-4-(thiobenzoylthio)pentanoic acid (1.35mmol) were then added to the mixture. Once the substance had fullydissolved, 67 mg of AIBN (0.41 mmol) were added. From then on, theconversion was regularly checked by means of HPLC.

When the conversion, based on methoxy polyethylene glycol methacrylate,had reached 80%, 14.81 g of [2-(methacryloyloxy)ethyl]trimethylammoniumchloride (0.054 mol) were added. The mixture was left to react for afurther 2 h and then to cool. A clear, reddish, aqueous solution wasobtained having a solids content of around 40 wt. % which was dilutedwith water to obtain a solids content of around 30 wt. %.

The comb polymer thus obtained is a block copolymer comprising a firstbock with about 20 side chain-nearing monomeric units, and a secondblock with about 40 cationic monomer units. This polymer is referred toas comb polymer P3.

1.4 Further Comb Polymers

Further comb polymers were produced in a similar manner. Thereby, themethoxy polyethylene glycol₁₀₀₀ methacrylate was replaced by methoxypolyethylene glycol methacrylate with different chain lengths (averagemolecular weight of 500 g/mol, 2′000 g/mol, 3′000 g/mol and 5′000 g/mol)and/or the [2-(methacryloyloxy)ethyl]trimethylammonium chloride(cationic monomer unit) was replaced by methacrylic acid (anionicmonomer unit).

The following chapter gives an overview about the comb polymers producedand their properties.

1.5 Overview of Comb Polymers

TABLE 1 Comb polymers Weight of Ionic No. MPEG-MA monomer Ratio P1 1′000g/mol none 0 P2* 1′000 g/mol none 0 P3 1′000 g/mol C 2 P4 2′000 g/molnone 0 P5 1′000 g/mol C 0.2 P6 2′000 g/mol C 0.2 P7 500 g/mol none 0 V1none C — MPEG-MA = methoxy polyethylene glycol methacrylate C =[2-(methacryloyloxy)ethyl]trimethylammonium chloride Ratio = number ofionic monomers/number of MPEG-MA monomers *= Produced by conventionalfree radical polymerization

2. Mineral Binder Compositions

2.1 Mortar Mixtures

The mortar mixture used for test purposes had the dry compositiondescribed in Table 2:

TABLE 2 Dry composition of mortar mixture Component Amount [g] Cement(CEM I 42.5 N; Normo 4; available 750 g from Holcim Schweiz) Limestonefiller 141 g Sand 0-1 mm 738 g Sand 1-4 mm 1107 g Sand 4-8 mm 1154 gBentonite (swelling clay) For proportions see results section

To make a mortar mixture, the sands, the limestone filler, the cementand bentonite (if added) were dry-mixed in a Hobart mixer for 1 minute.Within 30 seconds, the mixing water (ratio of water to cement w/c=0.49)was added and the mixture was mixed for a further 2.5 minutes. The totalwet mixing time was 3 minutes in each case.

Prior to the addition to the mortar mixture, the respective comb polymer(clay blocker) and plasticizer (Sika® ViscoCrete® 3082; available fromSika, Schweiz) were mixed into the mixing water (for proportions seeresults section). Sika® ViscoCrete® 3082 is a standard polycarboxylateether-based superplasticizer corresponding to a polymer P as describedabove.

These mortar compositions are referred to as MC.

2.2 Cement Pastes

The cement pastes used for test purposes were based on 100 g cement (CEMI 42.5 N; Normo 4; available from Holcim Schweiz), 5 g limestone fillerwith a grain size below 0.125 mm, bentonite (for proportions see resultssection) and water.

To make a cement paste, the cement/filler/bentonite mix was added to abeaker and, in another beaker, the mixing water into which therespective comb polymer (clay blocker) and plasticizer (Sika®ViscoCrete® 3082; available form Sika, Schweiz) had been mixedbeforehand (for proportions see results section), was added. Afterwardsthe cement/filler/bentonite mix was carefully poured into the beakercontaining the water, and the wet mix was mixed for 1 minute with apropeller IKA stirrer at 1000 rpm. As a reference the water to cementratio of the cement/filler paste including the PCE was adjusted to aflow of 10-12 cm.

These cement pastes are referred to as CP.

3. Testing Procedures

To determine the effectiveness of the clay-blocking comb polymers in themortar mixture, the dispersing effect of the plasticizer was determinedby measuring the flow table spread (ABM) of a series of mortar mixtureswas measured in accordance with EN 1015-3 at different times.

The effectiveness of the clay-blocking comb polymers in the cementpastes was determined similarly. However, in this case a mini slumpconus on a dry glass plate was used instead of the standard equipmentdefined in EN 1015-3.

The test for determining compressive strength (in MPa) was carried outon prisms (40×40×160 mm) in accordance with standard EN 12390-1 to12390-4.

Also, the temperature curve of the mineral binder compositions (mortarmixtures, cement pastes) was recorded as control of hydration andsetting behavior, respectively, after mixing. Thereby, the time to onsetof the global temperature maximum was determined as a measure of thesetting time.

The air content was measured according to EN 12350-7.

In the tests, all of the admixtures (clay blocker, plasticizer) havebeen added as aqueous solutions or dispersions with a content of activeingredients of 30 wt.-%. Bentonite was added as a powder.

4. Results

Table 3 gives an overview of a first series of tests conducted and theresults achieved. Experiments R1 to R5 are experiments conducted forcomparative purposes without the addition of a comb polymer according tothe invention.

TABLE 3 (all wt.-% are given with respect to the cement content in themineral binder composition) Experiment Components R1 R2 R3 R4 R5 E1 E2E3 E4 E5 Mineral binder MC MC MC MC MC MC MC MC MC MC compositionBentonite [wt. %] 0 1 1 1 1 1 1 1 1 1 Clay blocker — — B1 B2 V1 P1 P3 P4P5 P6 Proportion [wt.-%] 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Plasticizer[wt.-%] 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 w/c 0.44 0.44 0.44 0.440.44 0.44 0.44 0.44 0.44 0.44 FTS^(#) [mm] after  0 min 178 121 152 148153 177 183 154 166 155 30 min 151 115 137 145 135 157 167 142 145 14060 min 149 110 124 132 125 149 139 130 144 136 Air content [%] 3.5 3.23.3 2.9 2.3 2.5 3.5 3.1 3.2 3.0 Setting time [h] 12.3 10.5 12.3 11.311.7 12.2 11.2 10.8 11.0 10.5 Plasticizer = Sika ® ViscoCrete ® 3082 B1= MasterSuna SBS 3890 (BASF) B2 = Floerger Floquat FL 2250 (SNF sas,France) ^(#)= flow table spread according to EN 1015-3. The time “0 min”corresponds to the first measurement immediately after the mixing of themortar sample.

The data in Table 3 clearly shows that the inventive comb polymers arehighly effective clay blockers which are at least as effective as knownclay blockers. Additionally, with the inventive comb polymers theclay-blocking activity can be maintained for a long time on a ratherhigh level. Especially advantageous are the comb polymers P1 and P3,i.e. homopolymers of side chain-bearing monomers or block copolymers ofside chain-bearing monomers with cationic monomers. Thereby, combpolymer P3 with cationic monomer units is the most effective.

Table 4 shows the results of a second set of experiments with combpolymers differing in side chain length.

TABLE 4 (all wt.-% are given with respect to the cement content in themineral binder composition) Experiment Components R6 R7 E6 E7 E8 Mineralbinder MC MC MC MC MC composition Bentonite [wt. %] 0 1 1 1 1 Clayblocker — — P1 P4 P7 Proportion [wt.-%] 0.27 0.27 0.27 Plasticizer[wt.-%] 0.5 0.5 0.5 0.5 0.5 w/c 0.48 0.48 0.48 0.48 0.48 FTS^(#) [mm]after  0 min 187 148 188 186 170 30 min 173 137 173 167 155 60 min 168 —162 156 145 Air content [%] 2.4 2.4 2.6 2.5 2.6 Setting time [h] 16.013.3 13.2 12.8 15.3 Strength [MPa] after  1 day 19.3 20.0 18.3 19.8 19.028 days 45.7 44.5 48.3 49.1 44.8 Plasticizer = Sika ® ViscoCrete ® 3082^(#)= flow table spread according to EN 1015-3. The time “0 min”corresponds to the first measurement immediately after the making-up ofthe mortar sample.

As can be deduced from the results given in Table 4, comb polymers witha length of the side chains of at least 1′000 g/mol or higher are mostefficient when compared with comb polymers having different chainlengths.

Table 5 shows the results of a third set of experiments in which combpolymers are compared to single MPEG side chain molecules.

TABLE 5 (all wt.-% are given with respect to the cement content in themineral binder composition) Experiment Components R8 R9 R10 R11 R12 E9Mineral binder MC MC MC MC MC MC composition Bentonite [wt. %] 0 1 1 1 11 Clay blocker — — B3 B4 B5 P1 Proportion [wt.-%] 0.27 0.27 0.27 0.27Plasticizer [wt.-%] 0.5 0.5 0.5 0.5 0.5 0.5 w/c 0.48 0.48 0.48 0.48 0.480.48 FTS^(#) [mm] after  0 min 190 151 156 163 177 184 30 min 163 132140 143 147 156 60 min 153 — — — — 152 Air content [%] 2.5 2.2 2.2 2.32.2 2.3 Setting time [h] 13.5 12.7 13.3 12.8 13.0 13.3 Strength [MPa]after  1 day 22.1 21.6 21.7 22.0 21.2 22.5 Plasticizer = Sika ®ViscoCrete ® 3082 B3 = methoxy polyethylene glycol₁₀₀₀ (averagemolecular weight: 1′000 g/mol) B4 = methoxy polyethylene glycol₃₀₀₀(average molecular weight: 3′000 g/mol) B5 = methoxy polyethyleneglycol₅₀₀₀ (average molecular weight: 5′000 g/mol) ^(#)= flow tablespread according to EN 1015-3. The time “0 min” corresponds to the firstmeasurement immediately after the making-up of the mortar sample.

As evident from Table 5, single MPEG side chains are less effective whencompared with the inventive comb polymer P1.

Table 6 shows the results of a fourth set of experiments in which thedispersing effect of the inventive clay-blocking comb polymers iscompared to a standard PCE in cement pastes without swelling clays.

TABLE 6 (all wt.-% are given with respect to the cement content in themineral binder composition) Experiment Components R13 R14 E10 E11Mineral binder CP CP CP CP composition Bentonite [wt. %] — — — — Clayblocker — — P1 P3 Proportion [wt.-%] 0.5 0.5 Plasticizer [wt.-%] — 0.5 —— w/c 0.36 0.36 0.36 0.36 FTS^(#) [mm] after 0 min 65 113 67 67Plasticizer = Sika ® ViscoCrete ® 3082 ^(#)= flow table spread accordingto EN 1015-3 with mini slump conus (see above). The time “0 min”corresponds to the first measurement immediately after the mixing of themortar sample.

Thus, the clay-blocking comb polymers according to the present inventiondo not have any significant plasticizing effect. Similar results havebeen obtained in mortar mixtures MC.

Table 7 shows the results of a fifth set of experiments wherebydifferent clay blockers have been tested in mortar compositions withvarying clay contents. Thereby, all of the experiments VC1-VC14 havebeen performed with mortar mixture MC, a water to cement ratio (w/c) of0.44, 0.5 wt. % plasticizer (Sika® ViscoCrete® 3082) and (if added) 0.25wt. % of clay blocker as depicted in the second column of Table 7. Inexperiments VC13-VC14, the plasticizer has been omitted, so that onlythe water-reducing capability of P1 could be compared directly to B1 inthe absence of clay.

TABLE 7 (all wt.-% are given with respect to the cement content in themineral binder composition) Clay Bentonite FTS^(#) [mm] FTS Experimentblocker [wt. %] after 0 min. increase^(@) VC1 — 1.00 148 +29.7% VC2 0.66160 VC3 0.33 178 VC4 — 192 VC5 B1 1.00 190 +30.5% VC6 0.66 220 VC7 0.33244 VC8 — 248 (bleeding observed) VC9 P1 1.00 190 +11.6% VC10 0.66 198VC12 0.33 209 VC12 — 212 VC13⁺ P1 — 133 VC14⁺ B1 — 222 B1 = MasterSunaSBS 3890 (BASF) ^(#)= flow table spread according to EN 1015-3. The time“0 min” corresponds to the first measurement immediately after themaking-up of the mortar sample. ^(@)= relative increase of FTS withrespect to FTS with 1 wt. % Bentonite for a given clay blocker ⁺=without plasticizer

The data given in Table 7 show that the inventive comb polymers arehighly robust, i.e. the sensitivity to varying swelling clay contents israther low. Specifically, when decreasing the clay content from 1 wt. %to 0 wt. %, with the inventive comb polymer P1 as clay blocker, the FTSincreases only by 11.6%. With all of the other tested clay blocker B1,the increase in FTS is >30% and, thus, much higher in this range ofswelling clay contents. The much stronger increase of B1 (experimentVC14) can be explained by the significant stronger plasticizing effectof B1 itself (experiment VC14) compared to the inventive comb polymer P1(experiment VC13).

Table 8 compares the effectiveness of the inventive comb polymer P1,which was produced via a controlled free radical polymerization, and theinventive comb polymer P2, which was produced via conventionalfree-radical polymerization.

TABLE 8 (all wt.-% are given with respect to the cement content in themineral binder composition) Experiment Components R15 R16 E12 E13Mineral binder MC MC MC MC composition Bentonite [wt. %] 0 1 1 1 Clayblocker — — P1 P2 Proportion [wt.-%] 0.27 0.27 Plasticizer [wt.-%] 0.50.5 0.5 0.5 w/c 0.48 0.48 0.48 0.48 FTS^(#) [mm] after  0 min 190 151184 188 30 min 163 132 156 152 60 min 153 — 152 147 Air content [%] 2.52.2 2.3 2.4 Setting time [h] 13.5 12.7 13.3 12.5 Strength [MPa] after  1day 22.1 21.6 22.5 22.1 Plasticizer = Sika ® ViscoCrete ® 3082 ^(#)=flow table spread according to EN 1015-3. The time “0 min” correspondsto the first measurement immediately after the making-up of the mortarsample.

It is evident that both inventive polymers P1 and P2 having a similarside chain length of 1′000 g/mol show a similar clay-blockingeffectiveness, although they were produced with different polymerizationprocesses.

It will be appreciated by those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. The presently disclosedembodiments are therefore considered in all respects to be illustrativeand not restricting.

1. A comb polymer, in particular for use as a clay-inerting agent,comprising: a) at least one poly(alkylene oxide) side chain-bearingmonomer unit M1 without ionic groups, b) optionally at least onecationic monomer unit MC, c) optionally at least one anionic monomerunit MA, d) optionally, at least one non-ionic monomer unit M3, whereinthe molar ratio of the cationic monomer units MC to the sidechain-bearing monomer units M1 is equal to or less than 10, the molarratio of the anionic monomer units MA to the side chain-bearing monomerunits M1 is less than 1, and the molar ratio of the non-ionic monomerunits M3 to the side chain-bearing monomer units M1 is less than
 5. 2. Acomb polymer according to claim 1, wherein the side chain-bearingmonomer unit M1 includes a structure of the formula I

wherein R¹, and R², in each case independently, are H or an alkyl grouphaving 1 to 5 carbon atoms, R³, in each case independently, is H, analkyl group having 1 to 5 carbon atoms, or a group with formula—(CH₂)_(m)—[C═O]_(p)—X—R₄, m=0, 1 or 2, p=0 or 1, X, in each caseindependently, is —O— or —NH—, R⁸ is a group of the formula-[AO]_(n)—R^(a) where A=C₂- to C₄-alkylene, R^(a) is H, a C₁- toC₂₀-alkyl group, -cycloalkyl group or -alkylaryl group, and n=2-250. 3.A comb polymer according to claim 1, wherein the cationic monomer unitMC in the polymer includes or consists a monomer which has a structureof the formula II,

wherein R⁵, in each case independently, is -[D]_(d)-[E]_(e)—F, withD=—(COO)— and/or —(CONH)—, E=an alkylene group having 1 to 5 carbonatoms, F=—N⁺R¹⁰R¹¹R¹², —S⁺R¹⁰R₁₁R¹² and/or —P⁺R¹⁰R¹¹R¹², wherein R¹⁰,R¹¹ and R¹² are independently of one another H, an aliphatic hydrocarbonmoiety having 1 to 20 C atoms, a cycloaliphatic hydrocarbon moietyhaving 5 to 8 C atoms and/or an aryl moiety having 6 to 14 C atoms;whereby d=0 or 1, e=0 or 1, R⁶, R⁷ and R⁸, in each case independently,are H or an alkyl group having 1 to 5 carbon atoms.
 4. A comb polymeraccording to claim 1, wherein the anionic monomer unit MA in the polymerincludes or consists of a monomer which has a structure of the formulaIII,

wherein R¹³, in each case independently, is —COOM, —SO₂—OM, —O—PO(OM)₂and/or —PO(OM)₂, R¹⁴ and R¹⁵, in each case independently, are H or analkyl group having 1 to 5 carbon atoms, R¹⁶, in each case independently,are H, —COOM or an alkyl group having 1 to 5 carbon atoms, or where R¹³forms a ring together with R¹⁶ to give —CO—O—CO—, M independently fromeach other is H⁺, an alkali metal ion, an alkaline earth metal ion, adi- or trivalent metal ion, an ammonium ion and an organic ammoniumgroup.
 5. A comb polymer according to claim 1, wherein the non-ionicmonomer M3 has a structure of the formula IV,

wherein R^(5′), R^(6′), R^(7′) are the same as defined for R⁶, R⁷ andR⁸, and m′ and p′ are the same as defined for m and p as described abovein the context of the copolymer, Y, in each case independently, is achemical bond or —O—, Z, in each case independently, is a chemical bond,—O— or —NH—, R²⁰, in each case independently, is an alkyl group,cycloalkyl group, alkylaryl group, aryl group, hydroxyalkyl group oracetoxyalkyl group, each having 1-20 carbon atoms.
 6. A comb polymeraccording to claim 1, wherein the comb polymer, with respect to thetotal number of monomer units present in the comb polymer, comprises: a)95-100 mol-%, of the at least one poly(alkylene oxide) sidechain-bearing monomer unit M¹, b) 0-1 mol-%, of the at least onecationic monomer unit MC, c) 0-1 mol-%, of the at least one anionicmonomer unit MA, d) 0-1 mol-%, of the at least one non-ionic monomerunit M3.
 7. A comb polymer according to claim 1, wherein the combpolymer, with respect to the total number of monomer units present inthe comb polymer, comprises: a) 30-70 mol-%, of of the at least onepoly(alkylene oxide) side chain-bearing monomer unit M¹, and b) 0-1mol-%, of the at least one cationic monomer unit MC, c) 0-1 mol-%, ofthe at least one anionic monomer unit MA, d) 30-70%, of the at least onenon-ionic monomer unit M3.
 8. A comb polymer according to claim 1,wherein the comb polymer, with respect to the total number of monomerunits present in the comb polymer, comprises: a) 10-99 mol-%, of the atleast one poly(alkylene oxide) side chain-bearing monomer unit M¹, andb) 1-90 mol-%, of the at least one cationic monomer unit MC, c) 0-1mol-%, of the at least one anionic monomer unit MA, d) 0-75 mol-% or 0mol-%, of the at least one non-ionic monomer unit M3.
 9. A comb polymeraccording to claim 1, wherein the comb polymer consists of the at leastone poly(alkylene oxide) side chain-bearing monomer unit M1 and,optionally, the non-ionic monomer unit M3.
 10. A comb polymer accordingto claim 1, wherein the comb polymer consists of the at least onepoly(alkylene oxide) side chain-bearing monomer unit M1 and the at leastone cationic monomer unit MC.
 11. A comb polymer according to claim 1,wherein the comb polymer is a block polymer, whereby, at least 75 mol-%,of the total number of the at least one side chain-bearing monomer unitsM1 are arranged in a first block of the block copolymer and wherein theblock copolymer comprises a second block in which at least 75 mol-%, ofthe total number of the at least one cationic monomer units MC arearranged.
 12. A kit of parts comprising a comb polymer according toclaim 1 and a plasticizer for mineral binder compositions.
 13. Acomposition comprising a comb polymer according to claim 1 and furthercomprising a mineral binder, aggregates and/or swellable clays.
 14. Amethod comprising the steps of adding to a composition comprisingswellable clays (i) a comb polymer according to claim 1 and (ii) aplasticizer for mineral binder compositions.
 15. A method for inerting aswellable clay and/or for reducing or inhibiting adverse effects ofswellable clays on the effectiveness of dispersants in mineral bindercompositions, comprising adding the comb polymer according to claim 1 toa mineral binder composition.